Wind Speed measurment question

[keyable]

Hello!

I have Meteo tower 40m in height. On my meteo towerI have two anemometers one at height 10m and second at height of 40m. Near second anemometer I have wind vane for measuring wind direction.

I use 9200-Plus NRG logger for my data logging.

My goal is to build a wind farm with Vestas V90-3MW (hub height is 105m). So I take data ONLY FROM 40m wind vane and anemomenter, then with the help of WAsP software I predict wind statistical data for the height of 105m.

Could anybody tell me if my method of mesurments are correct and how can i improve it? Also does it give me accurate data from 40m to 105m?

Thank you!

[Mark Kelly]

Hello, this seems to currently be the most reasonable way forward, though it can depend on the terrain.

Vertically extrapolating from 40m to 105m (height ratio of ~2.6) has much less uncertainty that extrapolating from 10m to 105m (height ratio >10); you can see this in the Wind Energy article by Kelly+Troen (2016). That article gives a form to estimate the expected uncertainty, though I note that such estimation requires having a reasonable roughness length assignment and pretty simple terrain (otherwise the uncertainty increases, no matter what the method you use).
Further, doing vertical-shear extrapolation from a {10,40}m pair up to 105m is more uncertain (avoid it in this case), especially if the terrain is not uniform/flat [see/search e.g. for DTU report of Kelly from 2016 for this].

Cheers,
--Mark

[keyable]

Dear Mark,

Thank you very much for your response! I pretty much understood everything. Could you please explain in more details what do you mean by this sentence: "Further, doing vertical-shear extrapolation from a {10,40}m pair up to 105m is more uncertain (avoid it in this case), especially if the terrain is not uniform/flat" ?

By the way my investigated territory is on the ridge. It is full of hills, but there is big advantage for this territory, that there are NO TREES and building nearby. It is like many hills (with some flat parts) and smooth surface.
Cheers!
Lado

[kedx3mmn]

MET data of Malaysia (from NOAA) is measured at 10m. There is no other free data available for us to do the calculation. In that case, if I do calculations with the 10m data, would my calculations become totally invalid?

[Duncan]

Hi, were the data actually measured at 10m AGL, or were they downscaled to that height from some other simulation or measurement? Duncan.

[Niels Gylling Mortensen]

MET data of Malaysia (from NOAA) is measured at 10m. There is no other free data available for us to do the calculation. In that case, if I do calculations with the 10m data, would my calculations become totally invalid?

No, the software will certainly extrapolate these measurements for you, but the uncertainty will be higher than if you used a taller mast.

Other free data: you can always use the Global Wind Atlas as well, but this also carries a fairly high uncertainty in predictions of single wind turbines and farms, see this presentation: http://orbit.dtu.dk/en/publications/global-wind-atlas--validation-and-uncertainty(7c6ba0d3-49b5-4973-91ce-811c7bdd7ff8).html.

Best regards,
Niels